1. Field of the Invention
The present invention relates to a method for producing amino acid components from fish egg skin which is the skin of the hard roe of cod, herring, salmon, bonito and the like, said amino acid components being useful as physiologically active substances or nutrient enhancers.
2. Description of Related Art
Although fish wastes, such as fish meat, fish skin and fish bone, produced in conjunction with marine product processing are attempted to be utilized after being manufactured into fish powders, fish oils, feeds for the animal industry and fertilizers for agriculture, most of the fish egg skins produced during the processing of fish eggs and the marine processing are discarded as industrial wastes.
Moreover, for a method for utilizing fish and shellfish, the fish and shellfish are treated at high temperatures to inactivate autolytic enzymes contained in the fish and shellfish, and then constituent proteins are degraded with Bacillus subtilis proteases and Aspergillus oryzae proteases into peptide amino acids and free amino acids, whereby fish and shellfish extracts are obtained which are said to have pharmaceutical actions such as anti-ulcer action, insulin-like action and anti-hyperlipemia (cf. e.g., Patent Document 1).
Also, for methods for utilizing fish skins, fish bones and fish scales, considered is the method for treating the fish skins and the fish bones with proteases to give gelatin which will be utilized as a food material (e.g., see Patent Document 2), or the methods for utilizing, as a biomaterial for the medical use or a cosmetic material, collagen extracted from the fish scales (cf. e.g., Patent Document 3) and the fish skins (cf. e.g., Patent Document 4).
On the other hand, recent dry foods with a chili pepper taste for a side dish or as hors d'oeuvres for alcoholic beverages have been proposed, said dry foods which are produced by drying roe membranes of spiced walleye pollack eggs (“Mentaiko”; cf. e.g., Patent Document 5), but their commercial value as dry foods is questionable due to characteristics of the roe membrane of which the majority is made up of fiber protein.
Also, the present inventor has proposed a food seasoning with a Mentaiko flavor via enzymatically degrading Mentaiko-dipping sauces for the purpose of effectively utilizing the dipping sauces which are mass-produced (cf. e.g., Patent Document 6). This seasoning contains not only low molecular peptides and amino acid components produced from the degradation of proteins in the Mentaiko eggs and the skins thereof left in the dipping sauces, but also various mainly natural seasonings added for flavoring, and thus it would be expected as seasoning with Mentaiko taste.
However, concerning the utilization of fish egg skin per se produced in company with the utilization of various fish eggs, effective utilization thereof has not been proposed although most skins are made up of contractile proteins (myosins) which are myogenic fiber proteins (see Table 1: Ingredients of purified fish egg skin).
TABLE 1IngredientEdible part, per 100 gWater7.0gProtein71.4gLipidLess than 0.1 gAsh6.0gSugar15.6gDietary fiberLess than 0.5 g                [Patent Document 1]        JP-B-1-14885        [Patent Document 2]        JP-A-10-276680        [Patent Document 3]        JP-A-5-93000        [Patent Document 4]        JP-A-2000-50811        [Patent Document 5]        JP-A-10-57016        [Patent Document 6]        JP-2001-390691        [Non-Patent Document 1]        
Food Science and Technology Research (Japan), Vol. 40, No. 11